523 lines
17 KiB
Python
523 lines
17 KiB
Python
# sqlalchemy/ext/baked.py
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# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Baked query extension.
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Provides a creational pattern for the :class:`.query.Query` object which
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allows the fully constructed object, Core select statement, and string
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compiled result to be fully cached.
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"""
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from ..orm.query import Query
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from ..orm import strategies, attributes, properties, \
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strategy_options, util as orm_util, interfaces
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from .. import log as sqla_log
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from ..sql import util as sql_util
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from ..orm import exc as orm_exc
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from .. import exc as sa_exc
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from .. import util
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import copy
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import logging
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log = logging.getLogger(__name__)
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class BakedQuery(object):
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"""A builder object for :class:`.query.Query` objects."""
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__slots__ = 'steps', '_bakery', '_cache_key', '_spoiled'
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def __init__(self, bakery, initial_fn, args=()):
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self._cache_key = ()
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self._update_cache_key(initial_fn, args)
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self.steps = [initial_fn]
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self._spoiled = False
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self._bakery = bakery
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@classmethod
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def bakery(cls, size=200):
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"""Construct a new bakery."""
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_bakery = util.LRUCache(size)
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def call(initial_fn, *args):
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return cls(_bakery, initial_fn, args)
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return call
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def _clone(self):
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b1 = BakedQuery.__new__(BakedQuery)
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b1._cache_key = self._cache_key
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b1.steps = list(self.steps)
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b1._bakery = self._bakery
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b1._spoiled = self._spoiled
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return b1
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def _update_cache_key(self, fn, args=()):
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self._cache_key += (fn.__code__,) + args
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def __iadd__(self, other):
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if isinstance(other, tuple):
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self.add_criteria(*other)
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else:
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self.add_criteria(other)
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return self
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def __add__(self, other):
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if isinstance(other, tuple):
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return self.with_criteria(*other)
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else:
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return self.with_criteria(other)
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def add_criteria(self, fn, *args):
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"""Add a criteria function to this :class:`.BakedQuery`.
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This is equivalent to using the ``+=`` operator to
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modify a :class:`.BakedQuery` in-place.
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"""
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self._update_cache_key(fn, args)
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self.steps.append(fn)
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return self
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def with_criteria(self, fn, *args):
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"""Add a criteria function to a :class:`.BakedQuery` cloned from this one.
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This is equivalent to using the ``+`` operator to
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produce a new :class:`.BakedQuery` with modifications.
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"""
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return self._clone().add_criteria(fn, *args)
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def for_session(self, session):
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"""Return a :class:`.Result` object for this :class:`.BakedQuery`.
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This is equivalent to calling the :class:`.BakedQuery` as a
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Python callable, e.g. ``result = my_baked_query(session)``.
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"""
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return Result(self, session)
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def __call__(self, session):
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return self.for_session(session)
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def spoil(self, full=False):
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"""Cancel any query caching that will occur on this BakedQuery object.
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The BakedQuery can continue to be used normally, however additional
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creational functions will not be cached; they will be called
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on every invocation.
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This is to support the case where a particular step in constructing
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a baked query disqualifies the query from being cacheable, such
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as a variant that relies upon some uncacheable value.
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:param full: if False, only functions added to this
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:class:`.BakedQuery` object subsequent to the spoil step will be
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non-cached; the state of the :class:`.BakedQuery` up until
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this point will be pulled from the cache. If True, then the
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entire :class:`.Query` object is built from scratch each
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time, with all creational functions being called on each
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invocation.
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"""
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if not full:
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_spoil_point = self._clone()
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_spoil_point._cache_key += ('_query_only', )
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self.steps = [_spoil_point._retrieve_baked_query]
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self._spoiled = True
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return self
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def _retrieve_baked_query(self, session):
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query = self._bakery.get(self._cache_key, None)
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if query is None:
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query = self._as_query(session)
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self._bakery[self._cache_key] = query.with_session(None)
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return query.with_session(session)
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def _bake(self, session):
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query = self._as_query(session)
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context = query._compile_context()
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self._bake_subquery_loaders(session, context)
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context.session = None
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context.query = query = context.query.with_session(None)
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query._execution_options = query._execution_options.union(
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{"compiled_cache": self._bakery}
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)
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# we'll be holding onto the query for some of its state,
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# so delete some compilation-use-only attributes that can take up
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# space
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for attr in (
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'_correlate', '_from_obj', '_mapper_adapter_map',
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'_joinpath', '_joinpoint'):
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query.__dict__.pop(attr, None)
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self._bakery[self._cache_key] = context
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return context
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def _as_query(self, session):
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query = self.steps[0](session)
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for step in self.steps[1:]:
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query = step(query)
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return query
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def _bake_subquery_loaders(self, session, context):
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"""convert subquery eager loaders in the cache into baked queries.
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For subquery eager loading to work, all we need here is that the
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Query point to the correct session when it is run. However, since
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we are "baking" anyway, we may as well also turn the query into
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a "baked" query so that we save on performance too.
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"""
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context.attributes['baked_queries'] = baked_queries = []
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for k, v in list(context.attributes.items()):
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if isinstance(v, Query):
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if 'subquery' in k:
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bk = BakedQuery(self._bakery, lambda *args: v)
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bk._cache_key = self._cache_key + k
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bk._bake(session)
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baked_queries.append((k, bk._cache_key, v))
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del context.attributes[k]
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def _unbake_subquery_loaders(self, session, context, params):
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"""Retrieve subquery eager loaders stored by _bake_subquery_loaders
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and turn them back into Result objects that will iterate just
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like a Query object.
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"""
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for k, cache_key, query in context.attributes["baked_queries"]:
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bk = BakedQuery(self._bakery, lambda sess: query.with_session(sess))
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bk._cache_key = cache_key
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context.attributes[k] = bk.for_session(session).params(**params)
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class Result(object):
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"""Invokes a :class:`.BakedQuery` against a :class:`.Session`.
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The :class:`.Result` object is where the actual :class:`.query.Query`
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object gets created, or retrieved from the cache,
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against a target :class:`.Session`, and is then invoked for results.
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"""
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__slots__ = 'bq', 'session', '_params'
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def __init__(self, bq, session):
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self.bq = bq
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self.session = session
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self._params = {}
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def params(self, *args, **kw):
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"""Specify parameters to be replaced into the string SQL statement."""
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if len(args) == 1:
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kw.update(args[0])
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elif len(args) > 0:
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raise sa_exc.ArgumentError(
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"params() takes zero or one positional argument, "
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"which is a dictionary.")
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self._params.update(kw)
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return self
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def _as_query(self):
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return self.bq._as_query(self.session).params(self._params)
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def __str__(self):
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return str(self._as_query())
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def __iter__(self):
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bq = self.bq
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if bq._spoiled:
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return iter(self._as_query())
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baked_context = bq._bakery.get(bq._cache_key, None)
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if baked_context is None:
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baked_context = bq._bake(self.session)
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context = copy.copy(baked_context)
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context.session = self.session
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context.attributes = context.attributes.copy()
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bq._unbake_subquery_loaders(self.session, context, self._params)
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context.statement.use_labels = True
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if context.autoflush and not context.populate_existing:
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self.session._autoflush()
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return context.query.params(self._params).\
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with_session(self.session)._execute_and_instances(context)
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def first(self):
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"""Return the first row.
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Equivalent to :meth:`.Query.first`.
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"""
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bq = self.bq.with_criteria(lambda q: q.slice(0, 1))
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ret = list(bq.for_session(self.session).params(self._params))
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if len(ret) > 0:
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return ret[0]
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else:
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return None
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def one(self):
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"""Return exactly one result or raise an exception.
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Equivalent to :meth:`.Query.one`.
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"""
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ret = list(self)
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l = len(ret)
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if l == 1:
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return ret[0]
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elif l == 0:
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raise orm_exc.NoResultFound("No row was found for one()")
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else:
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raise orm_exc.MultipleResultsFound(
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"Multiple rows were found for one()")
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def one_or_none(self):
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"""Return one or zero results, or raise an exception for multiple
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rows.
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Equivalent to :meth:`.Query.one_or_none`.
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.. versionadded:: 1.0.9
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"""
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ret = list(self)
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l = len(ret)
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if l == 1:
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return ret[0]
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elif l == 0:
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return None
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else:
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raise orm_exc.MultipleResultsFound(
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"Multiple rows were found for one_or_none()")
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def all(self):
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"""Return all rows.
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Equivalent to :meth:`.Query.all`.
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"""
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return list(self)
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def get(self, ident):
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"""Retrieve an object based on identity.
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Equivalent to :meth:`.Query.get`.
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"""
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query = self.bq.steps[0](self.session)
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return query._get_impl(ident, self._load_on_ident)
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def _load_on_ident(self, query, key):
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"""Load the given identity key from the database."""
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ident = key[1]
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mapper = query._mapper_zero()
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_get_clause, _get_params = mapper._get_clause
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def setup(query):
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_lcl_get_clause = _get_clause
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q = query._clone()
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q._get_condition()
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q._order_by = None
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# None present in ident - turn those comparisons
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# into "IS NULL"
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if None in ident:
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nones = set([
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_get_params[col].key for col, value in
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zip(mapper.primary_key, ident) if value is None
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])
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_lcl_get_clause = sql_util.adapt_criterion_to_null(
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_lcl_get_clause, nones)
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_lcl_get_clause = q._adapt_clause(_lcl_get_clause, True, False)
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q._criterion = _lcl_get_clause
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return q
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# cache the query against a key that includes
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# which positions in the primary key are NULL
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# (remember, we can map to an OUTER JOIN)
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bq = self.bq
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# add the clause we got from mapper._get_clause to the cache
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# key so that if a race causes multiple calls to _get_clause,
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# we've cached on ours
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bq = bq._clone()
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bq._cache_key += (_get_clause, )
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bq = bq.with_criteria(setup, tuple(elem is None for elem in ident))
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params = dict([
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(_get_params[primary_key].key, id_val)
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for id_val, primary_key in zip(ident, mapper.primary_key)
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])
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result = list(bq.for_session(self.session).params(**params))
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l = len(result)
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if l > 1:
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raise orm_exc.MultipleResultsFound()
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elif l:
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return result[0]
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else:
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return None
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def bake_lazy_loaders():
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"""Enable the use of baked queries for all lazyloaders systemwide.
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This operation should be safe for all lazy loaders, and will reduce
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Python overhead for these operations.
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"""
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BakedLazyLoader._strategy_keys[:] = []
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properties.RelationshipProperty.strategy_for(
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lazy="select")(BakedLazyLoader)
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properties.RelationshipProperty.strategy_for(
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lazy=True)(BakedLazyLoader)
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properties.RelationshipProperty.strategy_for(
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lazy="baked_select")(BakedLazyLoader)
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strategies.LazyLoader._strategy_keys[:] = BakedLazyLoader._strategy_keys[:]
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def unbake_lazy_loaders():
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"""Disable the use of baked queries for all lazyloaders systemwide.
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This operation reverts the changes produced by :func:`.bake_lazy_loaders`.
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"""
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strategies.LazyLoader._strategy_keys[:] = []
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BakedLazyLoader._strategy_keys[:] = []
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properties.RelationshipProperty.strategy_for(
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lazy="select")(strategies.LazyLoader)
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properties.RelationshipProperty.strategy_for(
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lazy=True)(strategies.LazyLoader)
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properties.RelationshipProperty.strategy_for(
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lazy="baked_select")(BakedLazyLoader)
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assert strategies.LazyLoader._strategy_keys
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@sqla_log.class_logger
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@properties.RelationshipProperty.strategy_for(lazy="baked_select")
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class BakedLazyLoader(strategies.LazyLoader):
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def _emit_lazyload(self, session, state, ident_key, passive):
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q = BakedQuery(
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self.mapper._compiled_cache,
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lambda session: session.query(self.mapper))
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q.add_criteria(
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lambda q: q._adapt_all_clauses()._with_invoke_all_eagers(False),
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self.parent_property)
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if not self.parent_property.bake_queries:
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q.spoil(full=True)
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if self.parent_property.secondary is not None:
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q.add_criteria(
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lambda q:
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q.select_from(self.mapper, self.parent_property.secondary))
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pending = not state.key
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# don't autoflush on pending
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if pending or passive & attributes.NO_AUTOFLUSH:
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q.add_criteria(lambda q: q.autoflush(False))
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if state.load_path:
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q.spoil()
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q.add_criteria(
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lambda q:
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q._with_current_path(state.load_path[self.parent_property]))
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if state.load_options:
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q.spoil()
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q.add_criteria(
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lambda q: q._conditional_options(*state.load_options))
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if self.use_get:
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return q(session)._load_on_ident(
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session.query(self.mapper), ident_key)
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if self.parent_property.order_by:
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q.add_criteria(
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lambda q:
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q.order_by(*util.to_list(self.parent_property.order_by)))
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for rev in self.parent_property._reverse_property:
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# reverse props that are MANYTOONE are loading *this*
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# object from get(), so don't need to eager out to those.
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if rev.direction is interfaces.MANYTOONE and \
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rev._use_get and \
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not isinstance(rev.strategy, strategies.LazyLoader):
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q.add_criteria(
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lambda q:
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q.options(
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strategy_options.Load(
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rev.parent).baked_lazyload(rev.key)))
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lazy_clause, params = self._generate_lazy_clause(state, passive)
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if pending:
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if orm_util._none_set.intersection(params.values()):
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return None
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q.add_criteria(lambda q: q.filter(lazy_clause))
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result = q(session).params(**params).all()
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if self.uselist:
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return result
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else:
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l = len(result)
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if l:
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if l > 1:
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util.warn(
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"Multiple rows returned with "
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"uselist=False for lazily-loaded attribute '%s' "
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% self.parent_property)
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return result[0]
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else:
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return None
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@strategy_options.loader_option()
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def baked_lazyload(loadopt, attr):
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"""Indicate that the given attribute should be loaded using "lazy"
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loading with a "baked" query used in the load.
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"""
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return loadopt.set_relationship_strategy(attr, {"lazy": "baked_select"})
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@baked_lazyload._add_unbound_fn
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def baked_lazyload(*keys):
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return strategy_options._UnboundLoad._from_keys(
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strategy_options._UnboundLoad.baked_lazyload, keys, False, {})
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@baked_lazyload._add_unbound_all_fn
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def baked_lazyload_all(*keys):
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return strategy_options._UnboundLoad._from_keys(
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strategy_options._UnboundLoad.baked_lazyload, keys, True, {})
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baked_lazyload = baked_lazyload._unbound_fn
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baked_lazyload_all = baked_lazyload_all._unbound_all_fn
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bakery = BakedQuery.bakery
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